The present invention generally relates to welding and more particularly, to a welding torch employing a welding wire as a consumption or consumable electrode.
Commonly, when a consumption electrode is employed for a welding torch, electric current is fed to the electrode through a contact member held in contact with said electrode, and in the above case, a long service life for the welding torch has been required despite problems of severe abrasion or wear of the contact member. In order to cope with the problem as described above, there has conventionally been proposed an arrangement as shown, for example, in FIGS. 1 and 2.
More specifically, in a known welding torch disclosed in FIGS. 1 and 2, a first and second abrasion-resisting guide members 3a and 3b are provided along an electrode passage in a torch body 1' so as to be spaced with respect to each other, while a heat resisting and abrasion-resisting guide block 3c having a thickness smaller than a width of the electrode is provided at one side of the electrode passage between the guide members 3a and 3b. An electrode 17 is held between the guide block 3c and a contact member 7' having a thickness exceeding the width of the electrode, and is delivered being fed with electric current through the contact member 7', thereby to perform the welding operation. Accordingly, the contact member 7' is merely formed with a deep groove as shown in FIG. 2 even if it is worn out and thus, a welding operation may be performed without hindrance.
Incidentally, in an arc welding, the so-called stick phenomenon often takes place wherein the electrode tip end adheres to an item to be welded (not shown) during arc starting or during welding. In this case, resistance heating represented by I.sup.2 R is produced in a contact position between the contact member 7' and the electrode 17, i.e., between the current feeding position and welding position at the electrode tip end and thus, the electrode can be extremely softened to deformable state. In connection with the above, although the delivery of the electrode is arranged to be properly interrupted through detection, for example, of shortcircuit current, it is seldom that the delivery of the electrode is suspended immediately when the electrode tip end has been fused onto the item to be welded. Namely, even after the electrode tip end has been fused onto the item to be welded, the electrode in its extremely softened state is still delivered to a certain extent, onto the welding item. In the above case, since the second abrasion-resisting guide member 3b is disposed in a position closer to the end of the electrode 17 than the contact position between the contact member 7' and the electrode 17 as shown in FIG. 1, the extremely softened electrode to be delivered towards the welding item beyond the contact position, becomes as if it were set into a hole of the second abrasion-resisting guide member 3b to form a so-called stick phenomenon as shown in the two-dotted chain lines in FIG. 3, with the result that the feeding of the electrode must be suspended under the above condition in many cases. In such a case, it is a general practice to start the torch again after cutting off the electrode tip end automatically or manually upon formation of the stick phenomenon. However, the electrode cannot be fed towards the welding item due to the presence of that portion of the electrode set in the hold of the second abrasion-resisting guide member 3b as described above. Accordingly, it has generally been required to grasp the electrode tip end by cutting pliers or the like and to pull the electrode in the direction of X.sub.1 thereby to remove the set electrode portion. However, since the space between the tip end of the welding torch and the welding item is normally selected to be approximately 10 through 30 mm, the torch must be sufficiently retreated to pull out the electrode in the direction of X.sub.1, thus resulting in an inferior operability. Although sintered porcelain which is superior in abrasion resistance and heat resistance, is normally used as the guide members, the mechanical strength of such sintered porcelain is not very high, and thus, there are cases whereby the guide members are damaged during the forced removal of the set electrode portion as described above, thus resulting not only in an economic disadvantage, but also in the necessity of replacement of the guide member. Furthermore, in a arc welding operation using the consumption electrode, molten metal particles at high temperatures, i.e. the so-called sputter, are generally scattered, and in the welding torch having such a construction as shown in FIG. 1 through FIG. 3, the sputter tends to enter from an opening or the like into the passage of the electrode wire or sliding groove portion of the contact member, so that the delivering of the electrode wire or movability of the contact member may be interfered with. In the conventional welding torch as described above, the provision of a cover member may be used to prevent the sputter from entering the passage of the electrode wire and sliding groove portion of the contact member. However, in this case, it is difficult to manufacture a cover member to be applied to a narrow portion, thus requiring high manufacturing cost, and in addition, even when the cover member is provided, maintenance of the torch tip end portion cannot be effected sufficiently, thus resulting in poor operability.